untitled Copyright British Standard Provided by IHS under lice No reproduction or network ` , , ` ` ` , , , , ` ` ` ` ` ` , , ` , , ` , ` , , ` BRITISH STANDARD BS EN 60076 11 2004 Power transformers[.]
Trang 1Power transformers —
Part 11: Dry-type transformers
The European Standard EN 60076-11:2004 has the status of a British Standard
ICS 29.180
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Copyright British Standards Institution
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This British Standard was
published under the authority
of the Standards Policy and
This British Standard is the official English language version of
EN 60076-11:2004 It is identical with IEC 60076-11:2004 It supersedes
BS EN 60726:2003 which will be withdrawn on 1 July 2007
The UK participation in its preparation was entrusted to Technical Committee PEL/14, Power transformers, which has the responsibility to:
A list of organizations represented on this committee can be obtained on request to its secretary
Cross-references
The British Standards which implement international or European
publications referred to in this document may be found in the BSI Catalogue
under the section entitled “International Standards Correspondence Index”, or
by using the “Search” facility of the BSI Electronic Catalogue or of British
— aid enquirers to understand the text;
— present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed;
— monitor related international and European developments and promulgate them in the UK
Amendments issued since publication
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Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members
Ref No EN 60076-11:2004 E
English version
Power transformers Part 11: Dry-type transformers
This European Standard was approved by CENELEC on 2004-07-01 CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member
This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions
CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom
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– 2 –Foreword
The text of document 14/476/FDIS, future edition 1 of IEC 60076-11, prepared by IEC TC 14, Power
transformers, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 60076-11 on 2004-07-01
This European Standard supersedes EN 60726:2003
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical national standard or by endorsement (dop) 2005-04-01 – latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2007-07-01 Annex ZA has been added by CENELEC
Endorsement notice
The text of the International Standard IEC 60076-11:2004 was approved by CENELEC as a European
Standard without any modification
Copyright British Standards Institution
Trang 5`,,```,,,,````-`-`,,`,,`,`,,` -CONTENTS
1 Scope 6
2 Normative references 6
3 Terms and definitions 7
4 Service conditions 7
4.1 General 7
4.2 Normal service conditions 7
4.3 Electromagnetic compatibility (EMC) 8
4.4 Provision for unusual service conditions 8
4.5 Transport and storage conditions 9
5 Tappings 9
6 Connections 9
7 Ability to withstand short circuit 9
8 Rating 10
8.1 General 10
8.2 Rated power 10
8.3 Preferred values of rated power 10
8.4 Operation at higher than rated voltage 10
8.5 Operation with fan cooling 10
8.6 Operation in an enclosure 10
9 Rating plate 11
9.1 Rating plate fitted to the transformer 11
9.2 Rating plate fitted to the transformer enclosure 11
10 Identification according to cooling method 11
10.1 Identification symbols 11
10.2 Arrangement of symbols 12
11 Temperature-rise limits 12
11.1 Normal temperature-rise limits 12
11.2 Reduced temperature rises for transformers designed for high cooling air temperatures or special air cooling conditions 13
11.3 High altitude temperature rise correction 13
12 Insulation levels 13
12.1 General 13
12.2 Transformers for use at high altitudes 15
13 Climatic, environmental and fire behaviour classes 15
13.1 Climatic classes 15
13.2 Environmental classes 15
13.3 Fire behaviour classes 15
13.4 Test criteria for climatic, environmental and fire behaviour classes 16
14 General requirements for tests 16
15 Measurement of winding resistance (routine test) 16
16 Measurement of voltage ratio and check of phase displacement (routine test) 17
17 Measurement of short-circuit impedance and load loss (routine test) 17
18 Measurement of no-load loss and current (routine test) 17
19 Separate-source AC withstand voltage test (routine test) 17
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– 4 –20 Induced AC withstand voltage test (routine test) 17
21 Lightning impulse test (type test) 18
22 Partial discharge measurement (routine and special test) 18
22.1 General 18
22.2 Basic measuring circuit (typical only) 18
22.3 Calibration of the measuring circuit 18
22.4 Voltage application 19
22.5 Partial discharge acceptance levels 20
23 Temperature-rise test (type test) 21
23.1 General 21
23.2 Methods of loading 21
23.3 Winding temperature-rise correction for reduced current 24
23.4 Determination of steady state conditions 24
24 Measurement of sound level (special test) 24
25 Short-circuit test (special test) 25
26 Environmental test (special test) 25
26.1 General 25
26.2 Validity of the test 25
26.3 Testing procedure 25
27 Climatic test (special test) 26
27.1 Thermal shock test (special test) 26
27.2 Validity of the test 26
27.3 Thermal shock test for C1 class transformers 27
27.4 Thermal shock test for C2 class transformers 28
28 Fire behaviour test (special test) 28
28.1 General 28
28.2 Checking of corrosive and harmful gases emission 28
28.3 Fire behaviour test for F1 class transformer 29
28.4 Quantities to be measured and measuring devices 31
28.5 Calibration of the test chamber without test object 31
28.6 Test method 31
28.7 Test report 32
28.8 Criteria for evaluating the test results 32
29 Tolerances 33
30 Protection against direct contact 33
31 Degrees of protection provided by enclosures 33
32 Earthing terminal 33
33 Information required with enquiry and order 33
Annex A (informative) Installation and safety of dry-type transformers 36
Annex ZA (normative) Normative references to international publications with their corresponding European publications 38
Copyright British Standards Institution
Trang 7`,,```,,,,````-`-`,,`,,`,`,,` -Figure 1 – Basic measuring circuit for the partial discharge test for a single-phase
transformer 19
Figure 2 – Basic measuring circuit for the partial discharge test for a three-phase transformer 19
Figure 3 – Voltage application for routine partial discharge test 20
Figure 4 – Voltage application for special partial discharge test 20
Figure 5 – Example of back-to- back method – Single phase .23
Figure 6 – Example of back-to-back method – Three-phase 23
Figure 7 – Test chamber 34
Figure 8 – Test chamber details 35
Table 1 – Letter symbols 12
Table 2 – Winding temperature-rise limits 13
Table 3 – Insulation levels based on European practice 14
Table 4 – Insulation levels based on North American practice 14
Table 5 – sequence of tests 16
Table 6 – Dimensions of test chamber (see Figures 7 and 8) 30
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– 6 –POWER TRANSFORMERS – Part 11: Dry-type transformers
1 Scope
This part of IEC 60076 applies to dry-type power transformers (including auto-transformers) having values of highest voltage for equipment up to and including 36 kV and at least one winding operating at greater than 1,1 kV The standard applies to all construction technologies
This standard does not apply to:
– gas-filled dry type transformers where the gas is not air;
– single-phase transformers rated at less than 5 kVA;
– polyphase transformers rated at less than 15 kVA;
– instrument transformers (see IEC 60044 and IEC 60186);
– starting transformers;
– testing transformers;
– traction transformers mounted on rolling stock;
– flameproof and mining transformers;
– welding transformers;
– voltage regulating transformers;
– small power transformers in which safety is a special consideration
Where IEC standards do not exist for the transformers mentioned above or for other special transformers, this standard may be applicable as a whole or in parts
2 Normative references
The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition
of the referenced document (including any amendments) applies
IEC 60050 (all parts), International electrotechnical vocabulary (IEV)
IEC 60071 (all parts), Insulation co-ordination
IEC 60076-1:1993, Power transformers – Part 1: General
Amendment 1 (1999)
IEC 60076-2, Power transformers – Part 2: Temperature rise
IEC 60076-3, Power transformers – Part 3: Insulation levels, dielectric tests and external
clearances in air
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`,,```,,,,````-`-`,,`,,`,`,,` -IEC 60076-5, Power transformers – Part 5: Ability to withstand short-circuit
IEC 60076-10, Power transformers – Part 10: Determination of sound levels
IEC 60085, Thermal evaluation and classification of electrical insulation
IEC 60270, High-voltage test techniques – Partial discharge measurements
IEC 60332-3-10, Tests on electric cables under fire conditions – Part 3-10: Test for vertical
flame spread of vertically-mounted bunched wires or cables – Apparatus
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60905:1987, Loading guide for dry-type power transformers
IEC 61330, High-voltage/low voltage prefabricated substations
3 Terms and definitions
For the purpose of this part of IEC 60076, the following terms and definitions apply
totally enclosed dry-type transformer
transformer in an un-pressurised enclosure cooled by the circulation of the internal air
3.3
enclosed dry-type transformer
transformer in a ventilated enclosure cooled by the circulation of the external air
3.4
non-enclosed dry-type transformer
transformer supplied without a protective enclosure cooled by natural or forced air ventilation
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`,,```,,,,````-`-`,,`,,`,`,,` -EN 60076-11:2004
– 8 –4.2.2 Altitude
A height above sea level not exceeding 1 000 m
4.2.3 Temperature of cooling air
The temperature of cooling air not exceeding:
40 °C at any time;
30 °C monthly average of the hottest month;
20 °C yearly average
and not below:
–25 °C in the case of outdoor transformers;
–5 °C in the case of indoor transformers
where the monthly and yearly averages are as defined in 3.12 of IEC 60076-1
4.2.4 Wave-shape of supply voltage
A supply voltage of which the waveshape is approximately sinusoidal
NOTE This requirement is normally not critical in public supply systems but may have to be considered in installations with considerable converter loading In such cases, there is a conventional rule that the deformation shall neither exceed 5 % total harmonic content nor 1 % even harmonic content, see IEC 61000-2-4 Also note the importance of current harmonics for load loss and temperature rise, see IEC 61378-1
4.2.5 Symmetry of polyphase supply voltages
For three-phase transformers, a set of three-phase supply voltages which are approximately symmetrical
4.2.6 Humidity
The relative humidity of the surrounding air shall be less than 93 % No drops of water shall
be present on the surface of the coils
4.3 Electromagnetic compatibility (EMC)
Transformers shall be considered as passive elements in respect to emission and immunity to electromagnetic disturbances
4.4 Provision for unusual service conditions
The purchaser shall identify in his enquiry any service conditions not covered by the normal service conditions in 4.2 Examples of such conditions are:
– high or low ambient temperature outside the limits prescribed in 4.2.3;
– restricted ventilation;
– altitude in excess of the limit prescribed in 4.2.2;
– damaging fumes and vapours;
Trang 11`,,```,,,,````-`-`,,`,,`,`,,` -– excessive and abrasive dust;
– high harmonic content of the load current;
– distortion of the supply voltage waveform;
– fast transient overvoltages over the limits prescribed in 12.1 and Clause 21;
– associated power factor correction and method of capacitor switching to limit inrush current;
Supplementary requirements, within defined limits, for the rating and testing of transformers designed for other than normal service conditions listed in 4.2, such as high temperature of
cooling air or altitude above 1 000 m are given in 11.2 and 11.3
4.5 Transport and storage conditions
All transformers shall be suitable for transportation and storage at ambient temperatures down to –25 °C
The supplier shall be informed of anticipated high levels of shock, vibration and inclination during transportation to site
5 Tappings
The requirements in IEC 60076-1 Clause 5 applies The preferred tapping range is either:
± 5 % in steps of 2,5 % (5 tap positions);
be capable of carrying full phase rated current
7 Ability to withstand short circuit
Transformers shall fulfil the requirements in IEC 60076-5 If the purchaser requires a test to demonstrate this fulfilment, this shall be stated in the contract
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8.2 Rated power
The transformer shall have an assigned rated power for each winding which shall be marked
on the rating plate The transformer shall be fully rated when supplied in an enclosure The rated power refers to continuous loading This is a reference value for guarantees and tests concerning load losses, temperature rises and short-circuit impedance
NOTE A two-winding transformer has only one value of rated power, identical for both windings When the transformer has rated voltage applied to the primary winding, and rated current flows through the terminals of that winding, the transformer receives the relevant rated power for both windings
The rated power corresponds to continuous duty; nevertheless, dry-type transformers complying with this standard can be overloaded and guidance on overloads is given in IEC 60905
8.3 Preferred values of rated power
The preferred values shall be in accordance with 4.3 of IEC 60076-1 starting from 50 kVA
8.4 Operation at higher than rated voltage
Within the prescribed value of Um, a transformer shall be capable of service without damage under conditions of overfluxing where the ratio of voltage over frequency exceeds the corresponding ratio at rated voltage and rated frequency by no more than 5 %
NOTE This requirement is not meant to be systematically utilised in normal service The consequential increase in iron losses under these conditions will have adverse effects and such operation should be of limited duration This condition should be reserved for relatively rare cases of service under limited periods of time, for example emergency service or extreme peak loading
8.5 Operation with fan cooling
When additional cooling by means of fans is provided, the nominal power rating with and without fans shall be subject to agreement between purchaser and supplier
The rating plate shall indicate both the power rating without fans and the maximum power rating with fan cooling
Trang 139 Rating plate
9.1 Rating plate fitted to the transformer
Each transformer shall be provided with a rating plate of weatherproof material, fitted in a visible position, showing the items indicated below The entries on the plate shall be indelibly marked (that is, by etching, engraving, stamping or by a photo-chemical process)
g) number of phases;
h) rated power for each kind of cooling;
i) rated frequency;
j) rated voltages, including tapping voltages, if any;
k) rated currents for each kind of cooling;
t) fire behaviour class
The rated withstand voltages for all windings shall appear on the rating plate The principles
of the standard notation are illustrated in Clause 5 of IEC 60076-3
9.2 Rating plate fitted to the transformer enclosure
Each transformer enclosure shall be provided with a rating plate of weatherproof material, fitted in a visible position, showing the items indicated in 9.1 The entries on the plate shall be indelibly marked (that is, by etching, engraving, stamping or by a photo-chemical process)
10 Identification according to cooling method
Trang 14– A transformer designed for natural air ventilation is designated AN
– A transformer designed for natural air ventilation up to specified rating and with forced cooling to a higher rating is designated AN/AF
11 Temperature-rise limits
11.1 Normal temperature-rise limits
The temperature rise of each winding of the transformer, designed for operation at normal service conditions, shall not exceed the corresponding limit specified in Table 2 when tested
in accordance with Clause 23
The maximum temperature occurring in any part of the winding insulation system is called the hot-spot temperature The hot spot temperature shall not exceed the rated value of the hot-spot winding temperature specified in Table 1 of IEC 60905 This temperature could be measured, however an approximate value for practical purposes can be calculated by using
equation 1 in 4.2.4 of IEC 60905 with the values for Z and q given in 7.2 of IEC 60905
Components used as insulating material may be used separately or in combination providing that their temperature does not exceed the values given for the appropriate insulation system temperature in accordance with the requirements as prescribed in the left hand column of Table 2
The temperature of the core, metallic parts and adjacent materials shall not reach a value that will cause damage to any part of the transformer
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`,,```,,,,````-`-`,,`,,`,`,,` -Table 2 – Winding temperature-rise limits
Insulation system temperature
(see Note 1)
°C
Average winding temperature rise limits at rated current (see Note 2)
NOTE 1 Letters refer to the temperature classifications given in IEC 60085
NOTE 2 Temperature rise measured in accordance with Clause 23
11.2 Reduced temperature rises for transformers designed for high cooling air
temperatures or special air cooling conditions
When the transformer is designed for service where the temperature of the cooling air exceeds one of the maximum values specified in 4.2.3, the temperature rise limits shall be reduced by the same amount as the excess The values shall be rounded to the nearest whole number of K
Any site conditions that may either impose restrictions on the cooling air or produce high ambient air temperatures should be stated by the purchaser
11.3 High altitude temperature rise correction
Unless otherwise agreed upon between the supplier and the purchaser, for transformers designed for operation at an altitude greater than 1 000 m but tested at normal altitudes, the limits of temperature rise given in Table 2 shall be reduced by the following amounts for each
500 m by which the intended working altitude exceeds 1 000 m:
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– 14 –Table 3 – Insulation levels based on European practice
Rated lightning impulse withstand voltage
≤ 1,1 3,6 7,2 12,0 17,5 24,0 36,0
Table 4 – Insulation levels based on North American practice
Dielectric insulation levels for dry type transformers used on system with BILs 200 kV and below
Basic Lightning Impulse Insulation Levels (BILs)
in common use (peak value 1,2 μs) Max LL
kV
Low frequency voltage insulation level
Impulse chopped wave:
minimum time to flash over ( μ s) 1 1 1 1,3 2 2 1,8 2 2,3 2,7
1 = Optional higher levels where exposure to overvoltage occurs and higher protective margins are required
2 = Lower levels where surge arrester protective devices can be applied with lower spark-over levels
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Trang 17`,,```,,,,````-`-`,,`,,`,`,,` -12.2 Transformers for use at high altitudes
When the transformers are specified for operation at altitudes between 1 000 m and 3 000 m
above sea-level, but tested at normal altitude, the rated short duration separate source AC
withstand voltage shall be increased by 1 % for each 100 m above 1 000 m Above 3 000 m,
the insulation level shall be defined by agreement between supplier and purchaser
13 Climatic, environmental and fire behaviour classes
13.1 Climatic classes
Two climatic classes are defined:
Class C1: The transformer is suitable for operation at ambient temperature not below –5°C
but may be exposed during transport and storage to ambient temperatures down
Environmental conditions for dry-type transformers are identified in terms of humidity,
condensation, pollution and ambient temperature
NOTE These are important not only during service but also during storage before installation
With regard to humidity, condensation and pollution, three different environmental classes are
defined:
Class E0: No condensation occurs on the transformers and pollution is negligible This is
commonly achieved in a clean, dry indoor installation
Class E1: Occasional condensation can occur on the transformer (for example, when the
transformer is de-energised) Limited pollution is possible
Class E2: Frequent condensation or heavy pollution or combination of both
Special tests according to the procedure of Clause 26 shall confirm the conformity of E1 or E2
class transformers
13.3 Fire behaviour classes
Two fire behaviour classes are defined:
Class F0: There is no special fire risk to consider Except for the characteristics inherent in
the design of the transformer, no special measures are taken to limit flammability
Nevertheless, the emission of toxic substances and opaque smoke shall be
minimized
Class F1: Transformers subject to a fire hazard Restricted flammability is required The
emission of toxic substances and opaque smokes shall be minimised
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– 16 –Special tests according to the procedure of Clause 28 shall confirm the conformity of class F1
transformers
NOTE Measurements made in conformity with Clause 28 tend to result in a standard deviation ≤ 10 K
13.4 Test criteria for climatic, environmental and fire behaviour classes
When a transformer is declared as suitable for a combination of climatic, environmental and
fire behaviour classes, those tests which prove compliance with said classes, are to be
carried out on the same transformer in the sequence given in Table 5
The tests specified in Clauses 26, 27 and 28 shall be carried out as specified on one
transformer being representative of the design type
Table 5 – Sequence of tests
1 Thermal shock at –5 °C 27.3 Yes No - - - - -
2 Thermal shock at –25 °C 27.4 No Yes - - - - -
3 Condensation test 26.3.1 - - No Yes No - -
4 Condensation and
humidity penetration test
5 Fire behaviour test 28.3 - - - No Yes
14 General requirements for tests
New transformers shall be subjected to tests as specified in Clauses 15 to 23 Transformers
which have been in service may be tested in accordance with this specification but dielectric
test levels should be reduced to 80 %, however, the guarantee levels of the transformer when
new do not apply
Tests shall be made by the manufacturer or at an approved laboratory, unless otherwise
agreed between the supplier and the purchaser at the tender stage
Dielectric tests in accordance with Clauses 19, 20 and 21 shall be made with the transformer
at approximately the temperature of the test house
Tests shall be performed on a completely assembled transformer including relevant
accessories supplied
Tapped windings shall be connected on their principal tapping unless the supplier and the
purchaser agree otherwise
The test basis for all characteristics other than insulation is the rated condition, unless the
test Clause states otherwise
15 Measurement of winding resistance (routine test)
The test described in 10.2 of IEC 60076-1 applies
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`,,```,,,,````-`-`,,`,,`,`,,` -16 Measurement of voltage ratio and check of phase displacement (routine test)
The test described in 10.3 of IEC 60076-1 applies
17 Measurement of short-circuit impedance and load loss (routine test)
The test described in 10.4 of IEC 60076-1 applies
The reference temperature of the short-circuit impedance and load loss shall be the permitted average winding temperature rise as given in column 2 of Table 2 plus 20 °C
When a transformer has windings of different insulation system temperatures, the reference temperature relating to the winding having the higher insulation system temperature shall be used
18 Measurement of no-load loss and current (routine test)
The test described in 10.5 of IEC 60076-1 applies
19 Separate-source AC withstand voltage test (routine test)
The test described in Clause 11 of IEC 60076-3 applies
The test voltage shall be in accordance with Table 3 or Table 4 for the specified insulation level of the transformer,
The full test voltage shall be applied for 60 s between the winding under test and all the remaining windings, core, frame and transformer enclosure, connected to earth
20 Induced AC withstand voltage test (routine test)
The test described in 12.2.1 of IEC 60076-3 applies
The test voltage shall be twice the rated voltage
The duration of the test at full voltage shall be 60 s for any test frequency up to and including twice the rated frequency When the test frequency exceeds twice the rated frequency, the duration of the test shall be:
sfrequencytest
frequencyrated
120× , but not less than 15 s
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– 18 –21 Lightning impulse test (type test)
The test described in Clause 13 of IEC 60076-3 applies
The test voltage shall be in accordance with Table 3 or Table 4 for the specified insulation level of the transformer
The test impulse wave shape shall be 1,2 μs ± 30 %/50 μs ± 20 %
The test voltage shall be of negative polarity The test sequence per line terminal shall be one calibration impulse at a voltage between 50 % and 75 % of the full voltage followed by three impulses at full voltage
NOTE In dry-type transformers, the lightning impulse test can give rise to capacitive partial discharges in the air which do not endanger the insulation These partial discharges lead to changes in the current waveform, whilst the voltage waveform varies only slightly or not at all In this case, the separate source voltage withstand test and induced overvoltage withstand test should be repeated Taking into account the above statement, slight deviations
in current wave-form are not reasons for rejection
22 Partial discharge measurement (routine and special test)
22.2 Basic measuring circuit (typical only)
A basic measuring circuit for the partial discharge test is shown in Figures 1 and 2
In the Figures, a partial discharge-free high voltage capacitor, C of suitable voltage rating
(having a capacitance value large in comparison with the calibration generator capacitance,
C0) in series with a detection impedance, Zm, is connected to each of the high-voltage winding terminals
22.3 Calibration of the measuring circuit
Attenuation of the discharge pulses occurs both within the windings and in the measuring circuit Calibration is carried out as described in Annex A of IEC 60076-3, by injecting simulated discharge pulses from a standard discharge calibrator at the transformer high voltage winding terminals It is convenient if the calibration generator has a repetition frequency of the order of one impulse per half cycle of the power frequency used for the test
on the transformer
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Figure 1 – Basic measuring circuit for the partial discharge test
for a single-phase transformer
Figure 2 – Basic measuring circuit for the partial discharge test
for a three-phase transformer 22.4 Voltage application
The partial discharge measurement shall be carried out after all dielectric tests are completed The low-voltage winding shall be supplied from a three-phase or single-phase source, depending on whether the transformer itself is three-phase or single-phase The voltage shall be as nearly as possible of sine-wave form and of a frequency suitably increased above the rated frequency to avoid excessive excitation current during the test The procedure shall be as in 22.4.1 or 22.4.2
22.4.1 Three-phase transformers
22.4.1.1 Routine test
The following test shall be performed on all dry type transformers
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